Light transmission
Light transmissometer
%key transmissometerP06 units UPCTseries transmissometer
CalCOFI holds 619,519 values of it from 8,588 sampling events in one dataset, 1993–2026, from the surface to 3,630 m. At 200–500 m it has risen 20.82 per decade since 1993.R How far light travels through the water is set by the particles in it, most of them living or lately alive, so a clear cast and a turbid one are a statement about the plankton as much as about the light.C
- 619,519
- values
- 215
- flagged
i
215 of these 619,519 values (under 0.1 %) are flagged by their provider as questionable or bad. The Explorer, the climatology and its anomalies leave them out; do the same when you read the data yourself (cc_qual_ok_sql()in calcofi4r,qual_ok_sql()in calcofi4py). - 1993–2026
- years
- 1
- dataset
- 1–3,630 m
- depth
- every month
- months
Measured in
1 dataset
i
One row per series, one cell per year, darker with more values — the same strip the front
door draws per dataset and a species page draws per taxon. Each row is one dataset's own
measurement_type; the label is written once, in the title above.
i
One row per series, one cell per year, darker with more values — the same strip the front door draws per dataset and a species page draws per taxon. Each row is one dataset's own measurement_type; the label is written once, in the title above.
-
series
transmissometer· source columnx_miss· flag columntrans_qno bound declared no P01 concept 215 flagged
Explorera depth section vs normaldb-queryERDDAPThis page as JSON R · Python · Parquet
Every way in 8 ways · ERDDAP · Parquet · R · Python · JSON
Read from measurements.json of release v2026.11.05, written at release by calcofi4db::build_measurements_catalog() beside taxa.json. The catalog's index is /measurements/; the JSON-LD on this page is a schema.org/DefinedTerm in the NERC P01 term set with a PropertyValue per series.
ExplorerExplorer · a depth section vs normaldb-querySELECT * FROM read_json('…/v2026.11.05/catalog.json')
-- objects[] WHERE table = 'obs_env'
-- AND partition_value = 'transmissometer'library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "obs_env") |> filter(measurement_type %in% c("transmissometer"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM obs_env WHERE measurement_type IN ('transmissometer')").df()How it is measured CTD-mounted transmissometer (raw voltage)
The transmissometer's raw light-path voltage before the daily M/B calibration converts it to percent transmission. (calcofi.org CTD FAQ circa 2020)
CTD FAQ circa 2020 on calcofi.org ↗Why it matters 3 ways to say it
other ways to say why · 2
- Beam attenuation is used as a stand-in for the particles the water carries, including the ones sinking out of the sunlit layer. needs a citation before it can be the pick
- Wikipedia A transmissometer or transmissiometer is an instrument for measuring the extinction coefficient of the atmosphere and sea water, and for the determination of visual range. It operates by sending a narrow, collimated beam of energy through the propagation medium. Transmissometer · CC BY-SA 4.0 · rev. 1328380936
The record’s own history 7 depth bands against the 1993–2013 normal
Each year against the normal i
Deeper than the climatology reaches: 3,237 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
i
Deeper than the climatology reaches: 3,237 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
Units and range % · no bound declared declared · 215 flagged
% · P06 units UPCT
details
- bounds
- No physical bound is declared for this series in metadata/measurement_type.csv, so nothing is enforced at the ingest and the range below is simply what the release carries.
- observed
- CTD Cast Files
transmissometer-53.34 · median 86.28 · 114.2 % (5th–95th percentile 0–92.82) - flags
- CTD Cast Files
transmissometertrans_qon 617 of 619,519 rows:0402 ·8215; qual_ok keeps 619,304. The codes are this dataset's own vocabulary, uninterpreted. - baseline
- A monthly climatology exists for this measurement (the release's climatology table: 1993–2013, dataset × station × the cruise's month × 10 m bin), so the Explorer can draw anomalies against it rather than values.
The familiar scale i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
By depth · by month 1–3,630 m · every month
By depth i
Values per depth band at the release grain, one thin bar per series. The bands are the
record's own (0-10 … 2000+ m).
i
Values per depth band at the release grain, one thin bar per series. The bands are the record's own (0-10 … 2000+ m).
By month i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in
the months the ships sail.
i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in the months the ships sail.
Cite the release, v2026.11.05
Cite the release; each dataset's own citation, licence and DOI are on its page — CTD Cast Files. The Explorer's Share → Cite writes it for the view you make.